fix(python): skip license if not provided

[roryschadler]

Related: #21468, #21335

For a few years, the pyproject.toml license field was set to NoLicense when the spec did not provide another license. This value is not a valid SPDX identifier, however - as far as I can tell, there isn't any valid SPDX identifier for unlicensed code. (the Unlicense is NOT the same thing as UNLICENSED, ref).

When this field was under the [tool.poetry] table, this was fine - Poetry doesn't seem to validate that field, or at least it allows NoLicense. Poetry docs on license

However, this field was moved under the [project] table in #21268. Both poetry v2 and uv (via setuptools) validate the project.license field, to ensure it's a valid SPDX identifier. Because NoLicense is invalid, the build fails.

Because there doesn't seem to be a valid identifier matching the spirit of NoLicense, I chose to remove the field entirely if a license is not provided.

note: some unrelated files had formatting changes when I ran bin/generate-samples.sh, included in the second commit.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
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  Commit all changed files.
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[roryschadler]

cc @cbornet @tomplus @krjakbrjak @fa0311 @multani

[wing328]

lgtm. thanks for the PR

(samples just updated in the master. thanks for also updating the samples in this PR)